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use std::marker::PhantomData;

use reactive::*;

pub use self::ActivateError::*;

#[derive(PartialOrd, Ord, PartialEq, Eq, Debug)]
pub enum ActivateError<T> {
	SourceActivationError(SourceError),
	SlotActivationError(SlotError<T>),
	NotConnected,
}

impl<T> From<SourceError> for ActivateError<T> {
	fn from(error: SourceError) -> Self { SourceActivationError(error) }
}
impl<T> From<SlotError<T>> for ActivateError<T> {
	fn from(error: SlotError<T>) -> Self { SlotActivationError(error) }
}

/// Represents activator which have an opportunity to become connected one
pub struct DisconnectedActivator;

impl<T, S> Sink<T, S> for DisconnectedActivator where S: Source<T> {
	type Connected = SourceConnectedActivator<T, S>;
	fn connect_source(self, src: S) -> SourceConnectedActivator<T, S> {
		SourceConnectedActivator(src, PhantomData)
	}
}

impl<T, S> Signal<T, S> for DisconnectedActivator where S: Slot<T> {
	type Connected = SlotConnectedActivator<T, S>;
	fn connect_slot(self, slot: S) -> SlotConnectedActivator<T, S> {
		SlotConnectedActivator(slot, PhantomData)
	}
}

/// Activator connected to `Source`
pub struct SourceConnectedActivator<T, S>(S, PhantomData<(T, S)>) where S: Source<T>;

impl<T, S, U> Signal<T, S> for SourceConnectedActivator<T, U> where S: Slot<T>, U: Source<T> {
	type Connected = ConnectedActivator<T, U, S>;
	fn connect_slot(self, slot: S) -> ConnectedActivator<T, U, S> {
		ConnectedActivator(self.0, slot, PhantomData)
	}
}


/// Activator connected to `Slot`
pub struct SlotConnectedActivator<T, S>(S, PhantomData<(T, S)>) where S: Slot<T>;

impl<T, S, U> Sink<T, S> for SlotConnectedActivator<T, U> where S: Source<T>, U: Slot<T> {
	type Connected = ConnectedActivator<T, S, U>;
	fn connect_source(self, src: S) -> ConnectedActivator<T, S, U> {
		ConnectedActivator(src, self.0, PhantomData)
	}
}


/// Fully connected activator
pub struct ConnectedActivator<T, S, U>(S, U, PhantomData<(T, S, U)>) where S: Source<T>, U: Slot<T>;

impl<T, S, U> ConnectedActivator<T, S, U> where S: Source<T>, U: Slot<T> {
	/// transfer portion of data from connected `Source` to `Slot`
	pub fn activate(&self) -> Result<(), ActivateError<T>> {
		let (ref src, ref slt) = (&self.0, &self.1);
		let value = try!(src.pull());
		try!(slt.push(value));
		Ok(())
	}
}


pub struct Activator<T, S, U> where S: Slot<T>, U: Source<T> {
	slot: Option<S>,
	source: Option<U>,
	pd: PhantomData<T>
}


impl<'a, T, S, U> Signal<T, S> for &'a mut Activator<T, S, U> where S: Slot<T>, U: Source<T> {
	type Connected = ();
	fn connect_slot(self, slot: S) {
		self.slot = Some(slot);
	}
}

impl<'a, T, S, U> Sink<T, U> for &'a mut Activator<T, S, U> where S: Slot<T>, U: Source<T> {
	type Connected = ();
	fn connect_source(self, source: U) {
		self.source = Some(source);
	}
}

impl<T, S, U> Activator<T, S, U> where S: Slot<T>, U: Source<T> {
	pub fn new() -> Activator<T, S, U> {
		Activator{slot: None, source: None, pd: PhantomData}
	}

	pub fn activate(&self) -> Result<(), ActivateError<T>> {
		if let (&Some(ref src), &Some(ref slt)) = (&self.source, &self.slot) {
			let value = try!(src.pull());
			try!(slt.push(value));
			Ok(())
		} else {
			Err(NotConnected)
		}
	}
}